Management of Suspected or Confirmed Influenza During Flu Season
Antiviral treatment should be started as soon as possible for all patients with suspected or confirmed influenza who are hospitalized, have severe illness, are at high risk for complications, are under 2 years or over 65 years of age, or are pregnant/postpartum. 1
Diagnostic Testing
- RT-PCR or other molecular assays are preferred for diagnosing influenza in hospitalized patients due to their superior sensitivity 1
- Multiplex RT-PCR assays targeting a panel of respiratory pathogens should be used in immunocompromised patients 1
- Rapid influenza diagnostic tests (RIDTs) and immunofluorescence assays should not be used in hospitalized patients except when molecular assays are unavailable, and negative results should be confirmed with RT-PCR 1
- Viral culture should not be used for initial diagnosis as results are not available in time to inform clinical management 1
Antiviral Treatment Recommendations
Who Should Receive Antiviral Treatment
Initiate antiviral treatment as soon as possible for the following groups, regardless of influenza vaccination status 1, 2:
- Hospitalized patients with influenza, regardless of illness duration
- Outpatients with severe or progressive illness
- High-risk patients including those with chronic medical conditions and immunocompromised patients
- Children younger than 2 years and adults ≥65 years
- Pregnant women and those within 2 weeks postpartum
Consider antiviral treatment for previously healthy outpatients with suspected or confirmed influenza if they can be treated within 48 hours of symptom onset 1, 2
Antiviral Medication Selection and Dosing
Start treatment with a single neuraminidase inhibitor (NAI): oral oseltamivir, inhaled zanamivir, or intravenous peramivir 1, 2
For most patients, use standard FDA-approved doses rather than higher doses 1
For uncomplicated influenza in otherwise healthy ambulatory patients 1, 3, 4:
- Oseltamivir: 75 mg orally twice daily for 5 days (adults); pediatric dosing based on weight
- Zanamivir: 10 mg inhaled twice daily for 5 days
- Peramivir: single intravenous dose
For patients with renal impairment (creatinine clearance <30 mL/min), reduce oseltamivir dosage to 75 mg once daily 2, 3
Consider longer duration of antiviral treatment for immunocompromised patients or those hospitalized with severe lower respiratory tract disease 1, 2
Management of Complications
Bacterial Coinfection
- Investigate and empirically treat bacterial coinfection in patients with 1:
- Severe initial presentation (extensive pneumonia, respiratory failure, hypotension, fever)
- Clinical deterioration after initial improvement, particularly in those treated with antivirals
- Failure to improve after 3-5 days of antiviral treatment
Antibiotic Selection
For non-severe influenza-related pneumonia 1:
- Most patients can be treated with oral antibiotics
- Preferred choices: co-amoxiclav or a tetracycline
- Alternative choices: macrolide (clarithromycin/erythromycin) or respiratory fluoroquinolone
For severe influenza-related pneumonia 1:
- Use parenteral antibiotics immediately after diagnosis
- Preferred regimen: intravenous combination of broad-spectrum β-lactamase stable antibiotic (co-amoxiclav or cephalosporin) plus a macrolide
Special Considerations
- Avoid corticosteroid adjunctive therapy for treatment of influenza unless clinically indicated for other reasons 1, 2
- Do not routinely administer immunoglobulin preparations for treatment of seasonal influenza 1
- For intubated patients with concerns about gastric absorption, consider alternative administration routes for antivirals 5
- Monitor for antiviral resistance, especially in high-risk situations such as 1:
- Patients who develop influenza while on or immediately after NAI chemoprophylaxis
- Immunocompromised patients with persistent viral replication despite treatment
- Patients with severe influenza who don't improve with treatment
Common Pitfalls to Avoid
- Delaying antiviral treatment beyond 48 hours in high-risk patients - treatment should be initiated as soon as possible for maximum benefit 2, 6
- Relying on rapid diagnostic tests without confirming negative results with more sensitive molecular assays 1
- Using antibiotics in uncomplicated influenza without evidence of bacterial coinfection 2, 7
- Using corticosteroids routinely for influenza treatment, which has been associated with increased mortality and bacterial superinfection 5
- Underutilizing antivirals in outpatient settings - studies show that antiviral medications are often underprescribed even for high-risk patients who would benefit most 8